Today I took a long morning walk -- six miles or so over the Georgia hills, a good stretch of the legs. Much of this was along country backroads, but for two miles in the middle, it was along a two-lane highway. Logging trucks went roaring by, their wake turning the stagnant, humid air into a brief cyclone.

As one such truck tore past, the rush of air behind it whipped up a smell that some of you will know. I knew at once that some large animal was dead nearby, and sure enough, as the air settled the smell remained.

It grew stronger and stronger as I kept my pace, until off in the forest, just away from the road, I could see the corpse of a buck, bloated with the heat of late summer.

It had died of blunt force trauma, struck no doubt by one of those same trucks, limping off to die a few feet in the forest. I could tell this because it was not butchered, as a poacher would do. Anyone who has found where poachers keep court knows that deer who meet their end that way are found in a far worse condition. Heaps of gore are common, where unwanted hooves and organs, and sometimes the heads, are left to rot after venison is stripped from the bones.

The smell of death is a singular one. Anyone who has smelled it once strongly will know it again immediately. Like all smells, it is hard to put into words. It disgusts, and repels.

A scientific mind knows why. The smell is only the way that the human brain interprets certain chemicals, in certain quantities, touching certain nerves in the nose. The sense that comes with it is a chemical reaction in the brain. That we can smell it, and recognize it, is only a feat of engineering -- the work of evolution, no different for men as for any beast that smells.

What is interesting, to a philosopher, is that is smells bad. It is only a collection of chemicals, as is the breath of a rose: it might have smelled as sweet.

Evolution explains this too. For untold thousands of years, men -- aye, and beasts before we were men -- had no better protection than their senses against disease. However it arose, by mutation or design, those for whom rotting corpses smelled bad had an advantage. We shy from the bloated corpse, and it is well for us that we do: its flesh is putrid, harbors disease and deadly microbes, sickens and kills. No good comes from the association.

This is not the only thing about death that repels us. Return for a moment to the alternative scene, the one where a buck is killed by a poacher. It is clear why death smells bad, but why does the death of a butchered animal look worse than the death of one killed at a blow by a speeding truck?

There is a reason, but it is not as immediately obvious. We have been hunters since before the beginning, as far as Mankind is concerned. Why should it be true that the sight of a butchered animal should bother us? The sight of a steak does not: it makes us hungry. It is not the simple fact of blood, or flesh, or parts of an animal slashed and chopped to order. It is the encounter with an animal that was plainly slain by a predator.

To understand this factor of ourselves, we have to reach back to a time when we were not the top of the food chain. We have to remember that Man grew up with lions.

Nor was it only lions. Our brains carry memories more ancient than our species, and far more:

Marco Iacoboni and associates at the UCLA Ahmanson-Lovelace Brain Mapping Center used fMRI machines to observe the neural impact of Super Bowl ads in five volunteers.... For example, during a Fed Ex ad a caveman ends up being crushed by a dinosaur. Although subjects described the ad as funny, it also elicited a strong response in the amygdala, which governs responses to threats or fear. They may not have consciously experienced fear, but their brains were assessing the threat of that dinosaur.

We see the pile of gore, and something deep within us lights up in alarm. We are on guard, to see if we might be next.

All those ancient lessons are whispering in our minds at the sight of a corpse. They work on deep and secret parts of us. Yet there is still one more, the greatest secret of death magic. It is the mystery of the severed head.

Today, among Americans, only hunters have encountered this directly. It comes in the time when you are cleaning a kill. You cut the head from the body, and hold it in your hand. Though you slew the beast yourself, though your own knife did the cutting, seeing the head disjoined from the body is the most disquieting experience it is easy to know.

Indeed, the hunter finds, it is as if the whole power of the animal were in the head. The body, with the head set aside, no longer really resembles an animal at all. It is plainly dinner, and a hide to use as a blanket in winter.

We do not react to the severed leg as we do a severed head: a drumstick is a delight to the eye; the haunch of a deer or a pig both looks and smells fine as it roasts on the fire. Or think of a fish, if you have ever had one served as they serve it in China: with the head still attached. It is a very different experience to eat such a one, than to eat a fillet.

This is why some hunters take the heads of their beasts, and place them as trophies upon the wall. It is why the ancient Gael took the head of his famous and noble foe, and tied it by its own braids to his chariot as a warning to others. It is why the more ancient Celt built temples to the severed head, with alcoves and emplacements specially constructed for displaying honored skulls.

It is why we have legends of Mimir, and Celtic tales of other severed heads that spoke wisdom to the wise. They conversed with us from the realm of death; they kept the power of great men.

All these things move us at a level deeper than we know how to understand. It is easy to explain why the smell of death repels us. Though not so obvious for a hunting people, it is yet still possible to understand why the butchered corpse is more upsetting than the whole one. The power of the severed head, though, is not easy to explain. Yet it is just as universal among mankind.

Armed Liberal wrote about the problem of those who 'keep their hands clean,' never hunting, buying meat prepackaged and without an awareness of the moral cost. I disagree: there is no moral cost. We are monsters, who butcher though it creates mounds of gore: who sever heads, and find it moves us though we know not why.

But it isn't killing that makes us monsters. We are exactly that same kind of creature, whether we have ever killed or not.

The moral problem of 'the clean hands' is that it is an illusion. It makes people believe they are better than they are, and therefore that others can also be better than they can be. It creates a class of people who feel clean, because they have never felt blood on their hands.

Yet all these things arise from things buried deep in the genetic code. You cannot walk away from them. The failure to experience these things does not mean you would not react to them in just the same way as everyone else: it only means that you cannot understand how you would react, and how others do.

The man with clean hands is just the same as the hunter. It is only that he does not know it. He does not understand that part of his soul, as it lurks beyond his experience. He comes to believe that there is a kind of human that is and can be clean: perhaps that sweet, aged lady on the corner, who in her youth broke necks every night before dinner.

Failing to understand what Man really is, he opens himself more than is wise, and defends himself less. The man with the clean hands believes in diplomacy but not the force that makes diplomacy viable. He believes in staying clean, because he believes it makes him better than you. He does not understand that it only makes him blind.

This is not a call to amoralism, but precisely the opposite. It is a call for true morality, which can only begin with awareness of sin. It can only come from a recognition of how deep-set, how permanent, how personal sin is in each of us.

It is only in that way that we can begin to put real chains on sin: by recognizing the truth about it. We must learn to face the truth about ourselves, so that we can better ourselves: we must learn to face the truth about others, so we will recognize when murder is in their hearts.

In Zen Lessons: The Art of Leadership, translated by Thomas Cleary, there is a lesson to which my mind often returns. It is a lesson taught by a great master of early Zen Buddhism, called Chan in the Chinese. He had made a life given to fasting and simplicity, relinquishment and moderation. One day he visited a hermit, preparing a simple meal of rice:

The master said, "Why do crows fly away when they see a man?" The hermit was at a loss; finally he put the same question back to the Chan master. The master said, "Because I still have a murderous heart."

So do you. And so do I, and know it. For which cause I set guards on myself, chains of chivalry and courtesy, forgiveness in spite of anger. Our ancestors knew it, for which cause they learned to fight duels instead of wars, and make laws that legitimized violence in defense but not aggression.

Armed Liberal is right. Modern society has given many, for the first time, the problem of clean hands. It has yet to teach them how to overcome that problem.

Iran may teach them, soon. Al Qaeda has already tried, and failed. I counsel them, as he tried to do, to take up hunting: for this is a lesson that can only be grasped by hunting or by war. If you do not grasp it soon, war is coming to teach you. Yet there is still time, now, to learn the better way.